Display device having multiple transistors

ABSTRACT

Disclosed is a display device that is capable of being driven with low power consumption. A first thin-film transistor including a polycrystalline semiconductor layer and a second thin-film transistor including an oxide semiconductor layer are disposed in an active area, thereby reducing power consumption. At least one opening formed in a bending area is formed to have the same depth as any one of contact holes formed in the active area, thereby making it possible to form the opening and the contact holes through the same process and consequently simplifying the process of manufacturing the device. A second source electrode of the second thin-film transistor and a second gate electrode of the second thin-film transistor overlap each other with an upper interlayer insulation film interposed therebetween so as to form a first storage capacitor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/735,797 filed May 3, 2022, which is a continuation of U.S. patentapplication Ser. No. 17/005,061 filed on Aug. 27, 2020, which is acontinuation of U.S. patent application Ser. No. 16/210,926 filed onDec. 5, 2018, which claims priority to Republic of Korea PatentApplication No. 10-2017-0175054, filed on Dec. 19, 2017 in the KoreanIntellectual Property Office, each of which is incorporated herein byreference in its entirety.

BACKGROUND Field of the Technology

The present disclosure relates to a display device, and moreparticularly to a display device that is capable of being driven withlow power consumption.

Discussion of the Related Art

An image display device, which displays various kinds of information ona screen, is a core technology of the information and communication ageand is currently being developed with the aims of realizing a thinnerand lighter design, greater portability, and higher performance. Hence,flat panel display devices, which overcome the disadvantageously greatweight and volume of a cathode ray tube (CRT), are in the spotlight.

Examples of flat panel display devices include liquid crystal display(LCD) devices, plasma display panel (PDP) devices, organiclight-emitting display (OLED) devices, and electrophoretic display (ED)devices.

In recent years, personal electronic devices, to which the above flatpanel display devices are applied, have been actively developed in thedirection of becoming more portable and/or wearable. These portable orwearable devices require display devices that are capable of beingdriven with low power consumption. However, it is difficult tomanufacture display devices capable of being driven with low powerconsumption using current technology.

SUMMARY

Accordingly, the present disclosure is directed to a display device thatsubstantially obviates one or more problems due to limitations anddisadvantages of the related art.

An object of the present disclosure is to provide a display device thatis capable of being driven with low power consumption.

Additional advantages, objects, and features of the disclosure will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of thedisclosure. The objectives and other advantages of the disclosure may berealized and attained by the structure particularly pointed out in thewritten description and claims thereof, as well as the appendeddrawings.

To achieve these objects and other advantages and in accordance with thepurpose of the disclosure, as embodied and broadly described herein,there is provided a display device, in which a first thin-filmtransistor including a polycrystalline semiconductor layer and a secondthin-film transistor including an oxide semiconductor layer are disposedin an active area, thereby reducing power consumption, in which at leastone opening formed in a bending area is formed to have the same depth asany one of contact holes formed in the active area, thereby making itpossible to form the opening and the contact holes through the sameprocess and consequently simplifying the process of manufacturing thedevice, and in which a second source electrode of the second thin-filmtransistor and a second gate electrode of the second thin-filmtransistor overlap each other with an upper interlayer insulation filminterposed therebetween so as to form a first storage capacitor.

It is to be understood that both the foregoing general description andthe following detailed description of the present disclosure areexemplary and explanatory and are intended to provide furtherexplanation of the disclosure as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure, are incorporated in and constitute apart of this application, illustrate embodiment(s) of the disclosure,and together with the description serve to explain the principle of thedisclosure.

FIG. 1 is a plan view illustrating a display device according to oneembodiment of the present disclosure.

FIG. 2 is a cross-sectional view taken along line I-I′ in the displaydevice shown in FIG. 1 according to one embodiment of the presentdisclosure.

FIGS. 3A and 3B are plan views illustrating sub-pixels disposed in theactive area shown in FIG. 1 according to one embodiment of the presentdisclosure.

FIGS. 4A and 4B are plan views illustrating embodiments of a signal linkdisposed in the bending area shown in FIG. 1 according to one embodimentof the present disclosure.

FIGS. 5A and 5B are circuit diagrams for explaining each sub-pixel ofthe display device shown in FIG. 1 according to one embodiment of thepresent disclosure.

FIG. 6 is a plan view illustrating the sub-pixel shown in FIG. 5Baccording to one embodiment of the present disclosure.

FIG. 7 is a cross-sectional view taken along lines II-II′, III-III′,IV-IV′, V-V′ and VI-VI′ in the organic light-emitting display deviceshown in FIG. 6 according to one embodiment of the present disclosure.

FIGS. 8A to 8C are cross-sectional views illustrating other embodimentsof the storage capacitor shown in FIG. 7 .

FIGS. 9A and 9B are cross-sectional views illustrating other embodimentsof the bending area shown in FIG. 7 .

FIGS. 10A to 10M are cross-sectional views for explaining a method ofmanufacturing the organic light-emitting display device shown in FIG. 7.

DETAILED DESCRIPTION

Reference will now be made in detail to the preferred embodiments of thepresent disclosure, examples of which are illustrated in theaccompanying drawings.

FIG. 1 is a plan view of a display device according to the presentdisclosure, and FIG. 2 is a cross-sectional view of the display deviceaccording to the present disclosure.

The display device shown in FIGS. 1 and 2 includes a display panel 200,a gate-driving unit 202, and a data-driving unit 204.

The display panel 200 is divided into an active area AA provided on asubstrate 101 and a non-active area NA provided around the active areaAA. The substrate 101 is formed of a plastic material having flexibilityso as to be bendable. The substrate is formed of a material such as, forexample, polyimide (PI), polyethylene terephthalate (PET), polyethylenenaphthalate (PEN), PC (polycarbonate), polyethersulfone (PES),polyarylate (PAR), polysulfone (PSF), cyclic-olefin copolymer (COC), orthe like.

The active area AA displays an image through unit pixels arranged in amatrix form. Each of the unit pixels includes a red (R) sub-pixel, agreen (G) sub-pixel, and a blue (B) sub-pixel or includes a red (R)sub-pixel, a green (G) sub-pixel, a blue (B) sub-pixel, and a white (W)sub-pixel. For example, as shown in FIG. 3A, the red (R) sub-pixel, thegreen (G) sub-pixel, and the blue (B) sub-pixel may be arranged in a rowalong the same horizontal line. Alternatively, as shown in FIG. 3B, thered (R) sub-pixel, the green (G) sub-pixel and the blue (B) sub-pixelmay be spaced apart from each other so as to be arranged in the form ofa triangle.

Each sub-pixel includes at least one of a thin-film transistor includingan oxide semiconductor layer or a thin-film transistor including apolycrystalline semiconductor layer. A thin-film transistor including anoxide semiconductor layer and a thin-film transistor including apolycrystalline semiconductor layer have higher electron mobility than athin-film transistor including an amorphous semiconductor layer and aretherefore capable of providing high resolution and of being driven withlow power.

At least one of the data-driving unit 204 or the gate-driving unit 202may be disposed in the non-active area NA.

The gate-driving unit 202 drives a scan line of the display panel 200.The gate-driving unit 202 is embodied using at least one of a thin-filmtransistor including an oxide semiconductor layer or a thin-filmtransistor including a polycrystalline semiconductor layer. At thistime, the thin-film transistor of the gate-driving unit 202 is formedsimultaneously with at least one thin-film transistor disposed in eachsub-pixel in the active area AA during the same process.

The data-driving unit 204 drives a data line of the display panel 200.The data-driving unit 204 is attached to the non-active area NA by beingmounted on the substrate 101 in a chip form or by being mounted on asignal transmission film 206 in a chip form. As shown in FIGS. 4A and4B, a plurality of signal pads PAD is disposed in the non-active area NAfor electrical connection with the signal transmission film 206. Drivingsignals, which are generated from the data-driving unit 204, thegate-driving unit 202, a power source (not shown), and a timingcontroller (not shown), are supplied to a signal line disposed in theactive area AA through the signal pads PAD.

The non-active area NA includes a bending area BA for bending or foldingthe display panel 200. The bending area BA is an area that is bent sothat the components such as the signal pads PAD, the gate-driving unit202 and the data-driving unit 204, which do not function to display, arelocated at the bottom surface of the active area AA. The bending areaBA, as shown in FIG. 1 , is located in the upper portion of thenon-active area NA, which corresponds to a region between the activearea AA and the data-driving unit 204. Alternatively, the bending areaBA may be located in at least one of the upper portion, the lowerportion, the left portion, or the right portion of the non-active areaNA. Accordingly, in the entire screen of the display device, the areaoccupied by the active area AA is maximized, and the area occupied bythe non-active area NA is minimized.

A signal link LK is disposed in the bending area BA in order to connecteach of the signal pads PAD with a corresponding one of the signal linesdisposed in the active area AA. In the case in which the signal link LKis formed in the shape of a straight line that extends in a bendingdirection BD, the signal link LK may undergo the largest bending stress,and thus a crack or short-circuit may be formed in the signal link LK.In order to prevent this problem, the signal link LK of the presentdisclosure is formed such that the width thereof in a directionperpendicular to the bending direction BD is increased so as to minimizethe bending stress that is applied thereto. To this end, as shown inFIG. 4A, the signal link LK is formed in a zigzag shape or a sine waveshape. Alternatively, as shown in FIG. 4B, the signal link LK is formedsuch that a plurality of diamond shapes, each having a hollow centerportion, is arranged in a row while being connected to each other.

In addition, as shown in FIG. 2 , the bending area BA has therein atleast one opening 212 for facilitating bending of the bending area BA.The opening 212 is formed by eliminating a plurality of inorganicinsulation layers 210 from the bending area BA, which cause cracking inthe active area AA. When the substrate 101 is bent, bending stress iscontinuously applied to the inorganic insulation layers 210 disposed inthe bending area BA. The inorganic insulation layers 210 are lesselastic than an organic insulation material, and are thus vulnerable tocracking. The cracks formed in the inorganic insulation layers 210spread to the active area AA via the inorganic insulation layers 210,leading to defects in the lines and malfunction of the elements. Inorder to prevent this problem, at least one planarization layer 208,which is formed of an organic insulation material that is more elasticthan the inorganic insulation layers 210, is disposed in the bendingarea BA. The planarization layer 208 functions to mitigate bendingstress that occurs when the substrate 101 is bent, thereby preventingthe occurrence of cracks. The opening 212 formed in the bending area BAis formed through the same mask process as at least one of a pluralityof contact holes formed in the active area AA, whereby the structure andthe manufacturing process of the display device are simplified.

This display device, which can be simplified in structure andmanufacturing process, is applicable to a display device that requires athin-film transistor, such as a liquid crystal display device, anorganic light-emitting display device, or the like. Hereinafter, adescription of the embodiment of the present disclosure will be made.The following description is given on the assumption that theabove-described display device, which can be simplified in structure andmanufacturing process, is an organic light-emitting display device, byway of example.

As shown in FIGS. 5A and 5B, in the organic light-emitting displaydevice, each of the sub-pixels SP includes a pixel-driving circuit and alight-emitting element 130, which is connected with the pixel-drivingcircuit.

As shown in FIG. 5A, the pixel-driving circuit has a 2T1C structure thatincludes two thin-film transistors ST and DT and one storage capacitorCst. Alternatively, as shown in FIGS. 5B and 6 , the pixel-drivingcircuit has a 4T1C structure that includes four thin-film transistorsST1, ST2, ST3 and DT and one storage capacitor Cst. However, thestructure of the pixel-driving circuit is not limited to theaforementioned structures shown in FIGS. 5A and 5B, but thepixel-driving circuit may have various other structures.

In the pixel-driving circuit shown in FIG. 5A, the storage capacitor Cstconnects a gate node Ng and a source node Ns to maintain a substantiallyconstant voltage between the gate node Ng and the source node Ns duringthe light-emitting operation. There is provided a driving transistor DT,which includes a gate electrode, which is connected to the gate node Ng,a drain electrode, which is connected to the drain node Nd, and a sourceelectrode, which is connected to the light-emitting element 130. Thedriving transistor DT controls the magnitude of the driving current inresponse to the voltage between the gate node Ng and the source node Ns.There is further provided a switching transistor ST, which includes agate electrode, which is connected to a scan line SL, a drain electrode,which is connected to a data line DL, and a source electrode, which isconnected to the gate node Ng. The switching transistor ST is turned onin response to a scan control signal SC from the scan line SL, andsupplies data voltage Vdata from the data line DL to the gate node Ng.The light-emitting element 130 connects the source node Ns, which isconnected to the source electrode of the driving transistor DT, to a lowpotential supply line 162 to emit light in response to the drivingcurrent.

The pixel-driving circuit shown in FIG. 5B has substantially the sameconstruction as the pixel-driving circuit shown in FIG. 5A, except thata source electrode of a first switching transistor ST1 connected withthe data line DL is connected to the source node Ns and that a secondand a third switching transistors ST2 and ST3 are further provided. Aduplicate explanation of the same components will be omitted.

The first switching transistor ST1 shown in FIGS. 5B and 6 includes agate electrode 152, which is connected to a first scan line SL1, a drainelectrode 158, which is connected to the data line DL, a sourceelectrode 156, which is connected to the source node Ns, and asemiconductor layer 154, which forms a channel between the sourceelectrode 156 and the drain electrode 158. The first switchingtransistor ST1 is turned on in response to a scan control signal SC1from the first scan line SL1, and supplies data voltage Vdata from thedata line DL to the source node Ns.

The second switching transistor ST2 includes a gate electrode GE, whichis connected to a second scan line SL2, a drain electrode DE, which isconnected to a reference line RL, a source electrode SE, which isconnected to the gate node Ng, and a semiconductor layer ACT, whichforms a channel between the source electrode SE and the drain electrodeDE. The second switching transistor ST2 is turned on in response to ascan control signal SC2 from the second scan line SL2, and supplies areference voltage Vref from the reference line RL to the gate node Ng.

The third switching transistor ST3 includes a gate electrode GE, whichis connected to a light emission control line EL, a drain electrode DE,which is connected to a high potential supply line 172, a sourceelectrode SE, which is connected to the drain node Nd, and asemiconductor layer ACT, which forms a channel between the sourceelectrode SE and the drain electrode DE. The third switching transistorST3 is turned on in response to a light emission control signal EN fromthe light emission control line EL, and supplies a high potentialvoltage VDD from the high potential supply line 172 to the drain nodeNd.

Each of the high potential supply line 172 and the low potential supplyline 162, which are included in the pixel-driving circuit, is formed ina mesh shape so that at least two sub-pixels share the same supplylines. To this end, the high potential supply line 172 includes a firsthigh potential supply line 172 a and a second high potential supply line172 b, which intersect each other, and the low potential supply line 162includes a first low potential supply line 162 a and a second lowpotential supply line 162 b, which intersect each other.

The second high potential supply line 172 b and the second low potentialsupply line 162 b are arranged parallel to the data line DL. One secondhigh potential supply line 172 b is provided for at least twosub-pixels. One second low potential supply line 162 b is provided forat least two sub-pixels. As shown in FIGS. 5A and 5B, the second highpotential supply line 172 b and the second low potential supply line 162b are arranged parallel to each other in the lateral direction.Alternatively, as shown in FIG. 6 , the second high potential supplyline 172 b and the second low potential supply line 162 b are arrangedparallel to each other in the vertical direction so as to overlap eachother.

The first high potential supply line 172 a is electrically connected tothe second high potential supply line 172 b, and is arranged parallel tothe scan line SL. The first high potential supply line 172 a divergesfrom the second high potential supply line 172 b. The first highpotential supply line 172 a compensates for the resistance of the secondhigh potential supply line 172 b, whereby the voltage drop (IR drop) ofthe high potential supply line 172 is minimized.

The first low potential supply line 162 a is electrically connected tothe second low potential supply line 162 b, and is arranged parallel tothe scan line SL. The first low potential supply line 162 a divergesfrom the second low potential supply line 162 b. The first low potentialsupply line 162 a compensates for the resistance of the second lowpotential supply line 162 b, whereby the voltage drop (IR drop) of thelow potential supply line 162 is minimized.

As such, each of the high potential supply line 172 and the lowpotential supply line 162 is formed in a mesh shape. Therefore, thenumber of second high potential supply lines 172 b and second lowpotential supply lines 162 b, which are arranged in the verticaldirection, may be reduced, and a larger number of sub-pixels may bedisposed due to the reduced number of second high potential supply lines172 b and second low potential supply lines 162 b, so that the apertureratio and the resolution of the device are increased.

One of the transistors included in the pixel-driving circuit includes apolycrystalline semiconductor layer, and one of the remainingtransistors includes an oxide semiconductor layer. As shown in FIG. 7 ,the switching transistor ST of the pixel-driving circuit shown in FIG.5A is embodied by a first thin-film transistor 150 including apolycrystalline semiconductor layer 154, and the driving transistor DTis embodied by a second thin-film transistor 100 including an oxidesemiconductor layer 104. Each of the first switching transistor ST1 andthe third switching transistor ST3 of the pixel-driving circuits shownin FIGS. 5B and 6 is embodied by a first thin-film transistor 150including a polycrystalline semiconductor layer 154, and each of thesecond switching transistor ST2 and the driving transistor DT isembodied by a second thin-film transistor 100 including an oxidesemiconductor layer 104. As such, according to the present disclosure,the second thin-film transistor 100 including the oxide semiconductorlayer 104 is applied to the driving transistor DT of each sub-pixel, andthe first thin-film transistor 150 including the polycrystallinesemiconductor layer 154 is applied to the switching transistor ST ofeach sub-pixel, whereby power consumption is reduced.

The first thin-film transistor 150 shown in FIGS. 6 and 7 includes thepolycrystalline semiconductor layer 154, the first gate electrode 152,the first source electrode 156, and the first drain electrode 158.

The polycrystalline semiconductor layer 154 is formed on a lower bufferlayer 112. The polycrystalline semiconductor layer 154 includes achannel region, a source region, and a drain region. The channel regionoverlaps the first gate electrode 152, with a lower gate insulation film114 interposed between, and is formed between the first source electrode156 and the first drain electrode 158. The source region is electricallyconnected to the first source electrode 156 through a first sourcecontact hole 160S. The drain region is electrically connected to thefirst drain electrode 158 through a first drain contact hole 160D. Thepolycrystalline semiconductor layer 154 has higher mobility than theamorphous semiconductor layer, thereby exhibiting low energy/powerconsumption and improved reliability. Therefore, the polycrystallinesemiconductor layer 154 is suitable for application to the switchingtransistor ST of each sub-pixel and the gate-driving unit 202 fordriving the scan line SL. A multi-buffer layer 140 and the lower bufferlayer 112 are disposed between the polycrystalline semiconductor layer154 and the substrate 101. The multi-buffer layer 140 impedes thediffusion of moisture and/or oxygen that has permeated the substrate101. The multi-buffer layer 140 is formed in a manner such that siliconnitride (SiNx) and silicon oxide (SiOx) are alternately stacked. Thelower buffer layer 112 functions to protect the polycrystallinesemiconductor layer 154 by interrupting the spread of various kinds ofdefects from the substrate 101. The lower buffer layer 112 may be formedof a-Si, silicon nitride (SiNx), silicon oxide (SiOx), or the like.

The first gate electrode 152 is formed on the lower gate insulation film114. The first gate electrode 152 overlaps the channel region of thepolycrystalline semiconductor layer 154, with the lower gate insulationfilm 114 interposed therebetween. The first gate electrode 152 may be asingle layer or multiple layers formed of the same material as a lowerstorage electrode, for example, any one selected from the groupconsisting of molybdenum (Mo), aluminum (Al), chrome (Cr), gold (Au),titanium (Ti), nickel (Ni), neodymium (Nd), and copper (Cu), or an alloythereof. However, the disclosure is not limited thereto.

First lower interlayer insulation film 116 and second lower interlayerinsulation film 118, which are located on the polycrystallinesemiconductor layer 154, are configured as inorganic films that havehigher hydrogen particle content than an upper interlayer insulationfilm 124. For example, the first lower interlayer insulation film 116and the second lower interlayer insulation film 118 are formed ofsilicon nitride (SiNx) through a deposition process using ammonia (NH3)gas, and the upper interlayer insulation film 124 is formed of siliconoxide (SiOx). The hydrogen particles contained in the first lowerinterlayer insulation film 116 and the second lower interlayerinsulation film 118 diffuse into the polycrystalline semiconductor layer154 during a hydrogenation process, thereby allowing pores in thepolycrystalline semiconductor layer 154 to be filled with hydrogen.Accordingly, the polycrystalline semiconductor layer 154 is stabilized,thus preventing deterioration of the properties of the first thin-filmtransistor 150.

The first source electrode 156 is connected to the source region of thepolycrystalline semiconductor layer 154 through a first source contacthole 160S that penetrates the lower gate insulation film 114, the firstlower interlayer insulation film 116 and the second lower interlayerinsulation film 118, an upper buffer layer 122, and the upper interlayerinsulation film 124. The first drain electrode 158 faces the firstsource electrode 156 and is connected to the drain region of thepolycrystalline semiconductor layer 154 through a first drain contacthole 160D that penetrates the lower gate insulation film 114, the firstlower interlayer insulation film 116 and the second lower interlayerinsulation film 118, the upper buffer layer 122, and the upperinterlayer insulation film 124. Since the first source electrode 156 andthe first drain electrode 158 are positioned in the same plane and areformed of the same material as a storage supply line (not shown), thefirst source electrode 156, the first drain electrode 158 and thestorage supply line (not shown) may be formed at the same time throughthe same mask process.

After the activation and hydrogenation processes of the polycrystallinesemiconductor layer 154 of the first thin-film transistor 150, the oxidesemiconductor layer 104 of the second thin-film transistor 100 isformed. That is, the oxide semiconductor layer 104 is disposed on thepolycrystalline semiconductor layer 154. Accordingly, the oxidesemiconductor layer 104 is not exposed to the high-temperatureconditions of the activation and hydrogenation processes of thepolycrystalline semiconductor layer 154, thereby preventing damage tothe oxide semiconductor layer 104 and therefore improving reliability.

The second thin-film transistor 100 is disposed on the substrate 101 soas to be spaced apart from the first thin-film transistor 150. Thesecond thin-film transistor 100 includes a second gate electrode 102,the oxide semiconductor layer 104, a second source electrode 106, and asecond drain electrode 108.

The second gate electrode 102 overlaps the oxide semiconductor layer 104with an upper gate insulation pattern 146 interposed therebetween. Thesecond gate electrode 102 is formed in the same plane as the first highpotential supply line 172 a. That is, it is formed on the upper gateinsulation pattern 146 using the same material as the first highpotential supply line 172 a. Accordingly, the second gate electrode 102and the first high potential supply line 172 a may be formed through thesame mask process, and therefore the number of mask processes may bereduced.

The oxide semiconductor layer 104 is formed on the upper buffer layer122 so as to overlap the second gate electrode 102, thereby forming achannel between the second source electrode 106 and the second drainelectrode 108. The oxide semiconductor layer 104 is formed of oxideincluding at least one metal selected from the group consisting of Zn,Cd, Ga, In, Sn, Hf, and Zr. Since the second thin-film transistor 100including this oxide semiconductor layer 104 has higher electronmobility and lower off-current than the first thin-film transistor 150including the polycrystalline semiconductor layer 154, it is suitablefor application to the switching and driving thin-film transistors STand DT, in which an On-time period is short but an Off-time period islong.

The upper interlayer insulation film 124 and the upper buffer layer 122,which are disposed adjacent to the upper side and the lower side of theoxide semiconductor layer 104, are configured as inorganic films thathave lower hydrogen particle content than the lower interlayerinsulation films 116 and 118. For example, the upper interlayerinsulation film 124 and the upper buffer layer 122 are formed of siliconoxide (SiOx), and the lower interlayer insulation films 116 and 118 areformed of silicon nitride (SiNx). Accordingly, it is possible to preventhydrogen contained in the lower interlayer insulation films 116 and 118and hydrogen contained in the polycrystalline semiconductor layer 154from being diffused to the oxide semiconductor layer 104 during a heattreatment process performed on the oxide semiconductor layer 104.

Each of the second source electrode 106 and the second drain electrode108 may be a single layer or multiple layers formed on the upperinterlayer insulation film 124, and may be formed of any one selectedfrom the group consisting of molybdenum (Mo), aluminum (Al), chrome(Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and copper(Cu), or an alloy thereof. However, the disclosure is not limitedthereto.

The second source electrode 106 is connected to the source region of theoxide semiconductor layer 104 through a second source contact hole 110Sthat penetrates the upper interlayer insulation film 124. The seconddrain electrode 108 is connected to the drain region of the oxidesemiconductor layer 104 through a second drain contact hole 110D thatpenetrates the upper interlayer insulation film 124. The second sourceelectrode 106 and the second drain electrode 108 are formed so as toface each other with the channel region of the oxide semiconductor layer104 interposed between.

As shown in FIG. 7 , the storage capacitor Cst is formed in a mannersuch that the gate electrode 102 of the driving transistor and thesource electrode 106 of the driving transistor overlap each other withthe upper interlayer insulation film 124 interposed between.

Alternatively, as shown in FIGS. 8A to 8C, the storage capacitor Cst mayinclude two or more storage capacitors, which are connected in parallel.

The storage capacitor Cst shown in FIG. 8A includes a first storagecapacitor Cst1 and a second storage capacitor Cst2, which are connectedin parallel.

The first storage capacitor Cst1 is formed in a manner such that thegate electrode 102 of the driving transistor and the source electrode106 of the driving transistor overlap each other with the upperinterlayer insulation film 124 interposed between.

The second storage capacitor Cst2 is formed in a manner such that alight-shielding layer 178 and the gate electrode 102 of the drivingtransistor overlap each other with the first lower interlayer insulationfilm 116, the second lower interlayer insulation film 118, and the upperbuffer layer 122 interposed between. The light-shielding layer 178 iselectrically connected to the source electrode 106 of the drivingtransistor.

Accordingly, the first storage capacitor Cst1 and the second storagecapacitor Cst2 are connected in parallel such that one end of each ofthe first and second storage capacitors Cst1 and Cst2 is connected tothe gate electrode 102 of the driving transistor and the opposite endthereof is connected to the source electrode 106 of the drivingtransistor. As a result, the total capacitance of the storage capacitorshown in FIG. 8A may become greater than the total capacitance of thestorage capacitor shown in FIG. 7 .

The storage capacitor shown in FIG. 8B includes a first storagecapacitor Cst1 and a second storage capacitor Cst2, which are connectedin parallel.

The first storage capacitor Cst1 is formed in a manner such that thesecond gate electrode 102 and the second source electrode 106 overlapeach other with the upper interlayer insulation film 124 interposedtherebetween.

The second storage capacitor Cst2 is formed in a manner such that astorage electrode 170 and the second source electrode 106 overlap eachother with a protective film 166 interposed therebetween. At this time,the storage electrode 170 is electrically connected to the second gateelectrode 102.

The storage electrode 170 is disposed on the portion of the protectivefilm 166 that is exposed through a storage hole 168, and thereforeoverlaps the second source electrode 106 with only the protective film166 interposed therebetween. The storage electrode 170 is formed of thesame material as a pixel connection electrode 142. The second storagecapacitor Cst2 shown in FIG. 8B, in which the storage electrode 170 andthe second source electrode 106 overlap each other with thesingle-layered protective film 166 interposed therebetween, has agreater capacitance than the second storage capacitor Cst2 shown in FIG.8A, in which the second gate electrode 102 and the light-shielding layer178 overlap each other with the two- or more-layered insulation films116, 118 and 122 interposed therebetween.

As a result, the total capacitance of the storage capacitor shown inFIG. 8B may become greater than the total capacitance of the storagecapacitor shown in FIG. 8A.

The storage capacitor shown in FIG. 8C includes a first storagecapacitor Cst1, a second storage capacitor Cst2, and a third storagecapacitor Cst3, which are connected in parallel.

The first storage capacitor Cst1 is formed in a manner such that thesecond gate electrode 102 and the second source electrode 106 overlapeach other with the upper interlayer insulation film 124 interposedtherebetween.

The second storage capacitor Cst2 is formed in a manner such that thestorage electrode 170 and the second source electrode 106 overlap eachother with the protective film 166 interposed therebetween. The storageelectrode 170 is electrically connected to the second gate electrode102. The storage electrode 170 is disposed on the portion of theprotective film 166 that is exposed through the storage hole 168, andtherefore overlaps the second source electrode 106 with only theprotective film 166 interposed therebetween.

The third storage capacitor Cst3 is formed in a manner such that thelight-shielding layer 178 and the second gate electrode 102 overlap eachother with the first lower interlayer insulation film 116, the secondlower interlayer insulation film 118, and the upper buffer layer 122interposed therebetween. At this time, the light-shielding layer 178 iselectrically connected to the second source electrode 106.

Accordingly, the first to third storage capacitors Cst1, Cst2 and Cst3are connected in parallel such that one end of each of the first tothird storage capacitors Cst1, Cst2 and Cst3 is connected to the secondgate electrode 102 and the opposite end thereof is connected to thesecond source electrode 106. As a result, the total capacitance of thestorage capacitor shown in FIG. 8C may become greater than the totalcapacitance of the storage capacitor shown in FIG. 7 .

The light-emitting element 130 includes an anode 132, which is connectedto the second source electrode 106 of the second thin-film transistor100, at least one light-emitting stack 134, which is formed on the anode132, and a cathode 136, which is formed on the light-emitting stack 134.

The anode 132 is connected to the pixel connection electrode 142, whichis exposed through a second pixel contact hole 144 that penetrates aplanarization layer 128. The pixel connection electrode 142 is connectedto the second source electrode 106, which is exposed through a firstpixel contact hole 120 that penetrates the protective film 166 and afirst planarization layer 126.

The anode 132 is formed in a multi-layer structure including atransparent conductive film and an opaque conductive film having highreflection efficiency. The transparent conductive film is formed of amaterial having a relatively high work function, e.g. indium-tin-oxide(ITO) or indium-zinc-oxide (IZO), and the opaque conductive film isformed in a single-layer or multi-layer structure including any oneselected from the group consisting of Al, Ag, Cu, Pb, Mo, and Ti, or analloy thereof. For example, the anode 132 may be formed in a structuresuch that a transparent conductive film, an opaque conductive film and atransparent conductive film are sequentially stacked, or such that atransparent conductive film and an opaque conductive film aresequentially stacked. The anode 132 is disposed on the secondplanarization layer 128 so as to overlap the light emission regionprovided by a bank 138 as well as the circuit region in which the firstand second transistors 150 and 100 and the storage capacitor Cst (180)are disposed, whereby the light emission area is increased.

The light-emitting stack 134 is formed by stacking, on the anode 132, ahole-related layer, an organic emission layer, and an electron-relatedlayer, either in that order or in the reverse order. In addition, thelight-emitting stack 134 may include first and second light-emittingstacks, which face each other with a charge generation layer interposedbetween. In this case, an organic emission layer of any one of the firstand second light-emitting stacks generates blue light, and an organicemission layer of the remaining one of the first and secondlight-emitting stacks generates yellow-green light, with the result thatwhite light is generated via the first and second light-emitting stacks.Since the white light generated from the light-emitting stack 134 isintroduced into a color filter (not shown) disposed on thelight-emitting stack 134, a color image may be realized. Alternatively,it may be possible to realize a color image in a manner such that eachlight-emitting stack 134 generates colored light corresponding to eachsub-pixel without a separate color filter. That is, a light-emittingstack 134 of a red (R) sub-pixel may generate red light, alight-emitting stack 134 of a green (G) sub-pixel may generate greenlight, and a light-emitting stack 134 of a blue (B) sub-pixel maygenerate blue light.

The bank 138 may be formed so as to expose the anode 132. The bank 138may be formed of an opaque material (e.g. a black material) in order toprevent optical interference between neighboring sub-pixels. In thiscase, the bank 138 includes a light-blocking material formed of at leastone selected from among a color pigment, organic black and carbonmaterials.

The cathode 136 is formed on the top surface and the side surfaces ofthe light-emitting stack 134 so as to face the anode 132 with thelight-emitting stack 134 interposed therebetween. In the case in whichthe cathode 136 is applied to a top-emission-type organic light-emittingdisplay device, the cathode 136 is a transparent conductive film formedof, for example, indium-tin-oxide (ITO) or indium-zinc-oxide (IZO).

The cathode 136 is electrically connected with the low potential supplyline 162. As shown in FIGS. 5B and 6 , the low potential supply line 162includes the first low potential supply line 162 a and the second lowpotential supply lines 162 b, which intersect each other. As shown inFIG. 7 , the first low potential supply line 162 a is formed in the sameplane as the second gate electrode 102, that is, is formed on the uppergate insulation pattern 146 using the same material as the second gateelectrode 102. The second low potential supply line 162 b is formed inthe same plane as the pixel connection electrode 142, that is, is formedon the first planarization layer 126 using the same material as thepixel connection electrode 142. The second low potential supply line 162b is electrically connected to the first low potential supply line 162a, which is exposed through a first line contact hole 164 thatpenetrates the upper interlayer insulation film 124, the protective film166, and the first planarization layer 126.

As shown in FIGS. 5B and 6 , the high potential supply line 172, whichsupplies high potential voltage VDD that is higher than the lowpotential voltage VSS supplied through the low potential supply line162, includes the first high potential supply line 172 a and the secondhigh potential supply lines 172 b, which intersect each other. The firsthigh potential supply line 172 a, as shown in FIG. 7 , is formed in thesame plane as the second gate electrode 102, that is, is formed on theupper gate insulation pattern 146 using the same material as the secondgate electrode 102. The second high potential supply line 172 b isformed in the same plane as the second source electrode 106 and thesecond drain electrode 108, that is, is formed on the upper interlayerinsulation film 124 using the same material as the second sourceelectrode 106 and the second drain electrode 108. The second highpotential supply line 172 b is electrically connected with the firsthigh potential supply line 172 a, which is exposed through a second linecontact hole 174 that penetrates the upper interlayer insulation film124. The second high potential supply line 172 b overlaps the second lowpotential supply line 162 b with the protective film 166 and the firstplanarization layer 126 interposed therebetween. At this time, even whena pinhole is formed in the first planarization layer 126 formed of anorganic insulation material, the protective film 166 formed of aninorganic insulation material may prevent short-circuiting of the secondhigh potential supply line 172 b and the second low potential supplyline 162 b.

As shown in FIG. 7 , a signal link 176, which is connected to at leastone of the low potential supply line 162, the high potential supply line172, the data line DL, the scan line SL, or the light emission controlline EL, is disposed across the bending area BA, in which first andsecond openings 192 and 194 are formed. The first opening 192 exposesthe side surface of the upper interlayer insulation film 124 and the topsurface of the upper buffer layer 122. The first opening 192 is formedso as to have a depth d1 equal to the depth of at least one of thesecond source contact hole 110S or the second drain contact hole 110D.The second opening 194 exposes the side surface of each of themulti-buffer layer 140, the lower buffer layer 112, the lower gateinsulation film 114, the first lower interlayer insulation film 116, thesecond lower interlayer insulation film 118, and the upper buffer layer122. The second opening 194 is formed so as to have a depth d2 greaterthan or equal to the depth of at least one of the first source contacthole 160S or the first drain contact hole 160D. Accordingly, themulti-buffer layer 140, the lower buffer layer 112, the lower gateinsulation film 114, the first lower interlayer insulation film 116, thesecond lower interlayer insulation film 118, the upper buffer layer 122,and the upper interlayer insulation film 124 are eliminated from thebending area BA through the first and second openings 192 and 194. As aresult of elimination of a plurality of inorganic insulation layers 140,112, 114, 116, 118, 122 and 124, which cause cracks, from the bendingarea BA, it is possible to easily bend the substrate 101 without formingcracks.

The signal link 176, which is disposed in the bending area BA, as shownin FIG. 7 , may be formed together with the pixel connection electrode142 through the same mask process. In this case, the signal link 176 isformed in the same plane as the pixel connection electrode 142 using thesame material, that is, is formed on the first planarization layer 126and the substrate 101. In order to cover the signal link 176 formed onthe first planarization layer 126 and the substrate 101, the secondplanarization layer 128 is disposed on the signal link 176.Alternatively, instead of the second planarization layer 128, anencapsulation film or an inorganic encapsulation layer of anencapsulation stack, which is embodied by a combination of inorganic andorganic encapsulation layers, is disposed on the signal link 176.

As shown in FIGS. 9A and 9B, the signal link 176 may be formed togetherwith the source and drain electrodes 106, 156, 108 and 158 through thesame mask process. In this case, the signal link 176 is formed in thesame plane as the source and drain electrode 106, 156, 108 and 158 usingthe same material, that is, is formed on the upper interlayer insulationfilm 124, and is also formed on the substrate 101 so as to be broughtinto contact with the substrate 101. At this time, the signal link 176is formed on the side surface of the upper interlayer insulation film124 and the top surface of the upper buffer layer 122, which are exposedby the first opening 192, and is also formed on the side surfaces of themulti-buffer layer 140, the lower buffer layer 112, the lower gateinsulation film 114, the first lower interlayer insulation film 116, thesecond lower interlayer insulation film 118, and the upper buffer layer122, which are exposed by the second opening 194. Therefore, the signallink 176 is formed in a step shape. In order to cover the signal link176 formed in a step shape, at least one of the first planarizationlayer 126 or the second planarization layer 128 is disposed on thesignal link 176. Alternatively, instead of the first and secondplanarization layers 126 and 128, an encapsulation film or an inorganicencapsulation layer of an encapsulation stack, which is embodied by acombination of inorganic and organic encapsulation layers, is disposedon the signal link 176.

As shown in FIGS. 9A and 9B, the signal link 176 may be disposed on themulti-buffer layer 140. At this time, a portion of the multi-bufferlayer 140, which is located between the signal links 176, is eliminatedso as to facilitate bending without forming cracks, with the result thata trench 196, through which the substrate 101 is exposed, is formedbetween the signal links 176.

The trench 196 shown in FIG. 9A is formed so as to pass throughout aportion of the multi-buffer layer 140 and to extend to a predetermineddepth in a portion of the substrate 101 at a location between the signallinks 176. The first and second planarization layers 126 and 128 aredisposed on the signal links 176. The trench 196 shown in FIG. 9B isformed so as to pass throughout a portion of the protective film 166 anda portion of the multi-buffer layer 140 and to extend to a predetermineddepth in a portion of the substrate 101 at a location between the signallinks 176. The protective film 166 and the first and secondplanarization layers 126 and 128 are disposed on the signal links 176.At least one moisture-blocking hole (not shown) may be formed in thebending area BA so as to penetrate the first and second planarizationlayers 126 and 128. The moisture-blocking hole is formed in at least oneof the region between the signal links 176 or the upper portions of thesignal links 176. The moisture-blocking hole prevents external moisturefrom permeating the active area AA through at least one of the firstplanarization layer 126 or the second planarization layer 128 disposedon the signal link 176. An inspection line (not shown) for use in aninspection process is formed in the bending area BA so as to have thesame structure as one of the signal links 176 shown in FIGS. 7, 9A and9B.

As described above, the multi-buffer layer 140, the lower buffer layer112, the lower gate insulation film 114, the first lower interlayerinsulation film 116, the second lower interlayer insulation film 118,the upper buffer layer 122, and the upper interlayer insulation film 124are eliminated from the bending area BA through the first opening 192and second opening 194. As a result of elimination of a plurality ofinorganic insulation layers 140, 112, 114, 116, 118, 122 and 124, whichcause cracks, from the bending area BA, it is possible to easily bendthe substrate 101 without forming cracks in the bending area BA.

FIGS. 10A to 10M are cross-sectional views for explaining the method ofmanufacturing the organic light-emitting display device shown in FIG. 7.

Referring to FIG. 10A, the multi-buffer layer 140, the lower bufferlayer 112, and the polycrystalline semiconductor layer 154 aresequentially formed on the substrate 101.

Specifically, the multi-buffer layer 140 is formed in a manner such thatsilicon oxide (SiOx) and silicon nitride (SiNx) are stacked alternatelyat least once on the substrate 101. Subsequently, the lower buffer layer112 is formed in a manner such that SiOx or SiNx is deposited on theentirety of the surface of the multi-buffer layer 140. Subsequently, anamorphous silicon thin film is formed on the substrate 101, on which thelower buffer layer 112 has been formed, through a low-pressure chemicalvapor deposition (LPCVD) or plasma-enhanced chemical vapor deposition(PECVD) method. Subsequently, a polycrystalline silicon thin film isformed by crystallizing the amorphous silicon thin film. Subsequently,the polycrystalline silicon thin film is patterned through aphotolithography process and an etching process using a first mask so asto form the polycrystalline semiconductor layer 154.

Referring to FIG. 10B, the gate insulation film 114 is formed on thesubstrate 101, on which the polycrystalline semiconductor layer 154 hasbeen formed, and the first gate electrode 152 and the light-shieldinglayer 178 are formed on the gate insulation film 114.

Specifically, the gate insulation film 114 is formed in a manner suchthat an inorganic insulation material such as SiNx or SiOx is depositedon the entirety of the surface of the substrate 101, on which thepolycrystalline semiconductor layer 154 has been formed. Subsequently, afirst conductive layer is deposited on the entirety of the surface ofthe gate insulation film 114 and is then patterned through aphotolithography process and an etching process using a second mask soas to form the first gate electrode 152 and the light-shielding layer178. Subsequently, the polycrystalline semiconductor layer 154 is dopedwith impurities through a doping process using the first gate electrode152 as a mask, thereby forming the source and drain regions, which donot overlap the first gate electrode 152, and the channel region, whichoverlaps the first gate electrode 152.

Referring to FIG. 10C, at least one layered first lower interlayerinsulation film 116, at least one layered second lower interlayerinsulation film 118 and the upper buffer layer 122 are sequentiallyformed on the substrate 101, on which the first gate electrode 152 andthe light-shielding layer 178 have been formed. The oxide semiconductorlayer 104 is formed on the upper buffer layer 122.

Specifically, the first lower interlayer insulation film 116 is formedin a manner such that an inorganic insulation material such as SiNx orSiOx is deposited on the entirety of the surface of the substrate 101,on which the first gate electrode 152 and the light-shielding layer 178have been formed. The second lower interlayer insulation film 118 isformed in a manner such that an inorganic insulation material such asSiNx or SiOx is deposited on the entirety of the surface of the firstlower interlayer insulation film 116. Subsequently, the upper bufferlayer 122 is formed in a manner such that an inorganic insulationmaterial such as SiNx or SiOx is deposited on the entirety of thesurface of the second lower interlayer insulation film 118.Subsequently, the oxide semiconductor layer 104 is deposited on theentirety of the surface of the upper buffer layer 122, and is thenpatterned through a photolithography process and an etching processusing a third mask so as to form the oxide semiconductor layer 104,which overlaps the light-shielding layer 178.

Referring to FIG. 10D, the upper gate insulation pattern 146, the secondgate electrode 102, the first low potential supply line 162 a, and thefirst high potential supply line 172 a are formed on the substrate 101,on which the oxide semiconductor layer 104 has been formed.

Specifically, the upper gate insulation film is formed on the substrate101, on which the oxide semiconductor layer 104 has been formed, and athird conductive layer is formed through a deposition method such assputtering. The upper gate insulation film is formed of an inorganicinsulation material such as SiOx or SiNx. The third conductive layer mayhave a single-layer structure or a multi-layer structure, and may beformed of a metal material such as, for example, Mo, Ti, Cu, AlNd, Al,or Cr, or an alloy thereof. Subsequently, the third conductive layer andthe upper gate insulation film are patterned at the same time through aphotolithography process and an etching process using a fourth mask,with the result that the upper gate insulation pattern 146 is formedunder each of the second gate electrode 102, the first low potentialsupply line 162 a, and the first high potential supply line 172 a so asto have the same pattern as each of the second gate electrode 102, thefirst low potential supply line 162 a, and the first high potentialsupply line 172 a. At this time, during the dry etching of the uppergate insulation film, the oxide semiconductor layer 104, which does notoverlap the second gate electrode 102, is exposed by plasma, and oxygenin the oxide semiconductor layer 104 exposed by plasma is eliminatedthrough reaction to plasma gas. Accordingly, the oxide semiconductorlayer 104, which does not overlap the second gate electrode 102, becomesconductive and becomes the source and drain regions.

Referring to FIG. 10E, the upper interlayer insulation film 124, whichhas the first opening 192, the first source contact hole 160 s and thesecond source contact hole 110S, the first drain contact hole 160D andthe second drain contact holes 110D and the first line contact hole 165and the second line contact hole 174, is formed on the substrate 101, onwhich the upper gate insulation pattern 146, the second gate electrode102, the first low potential supply line 162 a and the first highpotential supply line 172 a have been formed.

Specifically, the upper interlayer insulation film 124 is formed in amanner such that an inorganic insulation material such as SiNx or SiOxis deposited on the entirety of the surface of the substrate 101, onwhich the upper gate insulation pattern 146, the second gate electrode102 and the first high potential supply line 172 have been formed.Subsequently, the upper interlayer insulation film 124 is patternedthrough a photolithography process and an etching process using a fifthmask so as to form the first source contact hole 160 s and the secondsource contact hole 110S, the first drain contact hole 160D and thesecond drain contact holes 110D, and the first line contact hole 165 andthe second line contact hole 174. At the same time, the upper interlayerinsulation film 124 is eliminated from the bending area BA so as to formthe first opening 192. The first source contact hole 160 s and thesecond source contact hole 110S, the first drain contact hole 160D andthe second drain contact holes 110D, the first line contact hole 165 andthe second line contact hole 174, and the first opening 192 are formedso as to penetrate the upper interlayer insulation film 124.Accordingly, the first opening 192 has a depth equal to the depth of atleast one of the first source contact hole 160S, the second sourcecontact hole 110S, the first drain contact hole 160D, the second draincontact hole 110D, the first line contact hole 164, or the second linecontact hole 174.

Referring to FIG. 10F, the second opening 194 is formed in the bendingarea BA on the substrate 101, on which the upper interlayer insulationfilm 124 has been formed. At the same time, the gate insulation film114, the first lower interlayer insulation film 116 and second lowerinterlayer insulation film 118, and the upper buffer layer 122 areeliminated from the first source contact hole 160S and the first draincontact hole 160D.

Specifically, the lower gate insulation film 114, the first lowerinterlayer insulation film 116 and second lower interlayer insulationfilm 118, and the upper buffer layer 122 are eliminated from the firstsource contact hole 160S and the first drain contact hole 160D throughan etching process, in which a photoresist pattern, which is formed onthe substrate 101 on which the upper interlayer insulation film 124 hasbeen formed through a photolithography process using a sixth mask, isused as a mask. At the same time, the multi-buffer layer 140, the lowerbuffer layer 112, the lower gate insulation film 114, the first lowerinterlayer insulation film 116 and second lower interlayer insulationfilm 118, and the upper buffer layer 122 are eliminated from the bendingarea BA so as to form the second opening 194. Upon the formation of thesecond opening 194, a portion of the substrate 101 may also beeliminated.

Referring to FIG. 10G, the first source electrode 156 and the secondsource electrode 106, the first drain electrode 158 and the second drainelectrode 108, and the second high potential supply line 172 b areformed on the substrate 101, on which the second opening 194 has beenformed.

Specifically, a fourth conductive layer, which is formed of Mo, Ti, Cu,AlNd, Al or Cr, or an alloy thereof, is deposited on the entirety of thesurface of the substrate 101, on which the second opening 194 has beenformed. Subsequently, the fourth conductive layer is patterned through aphotolithography process and an etching process using a seventh mask soas to form the first source electrode 156 and the second sourceelectrode 106, the first drain electrode 158 and the second drainelectrode 108, and the second high potential supply line 172 b.

Referring to FIG. 10H, the protective film 166 having therein the firstpixel contact hole 120 is formed on the substrate 101, on which thefirst source electrode 156 and the second source electrode 106, thefirst drain electrode 158 and the second drain electrode 108, and thesecond high potential supply line 172 b have been formed.

Specifically, the protective film 166 is formed in a manner such that aninorganic insulation material such as SiNx or SiOx is deposited on theentirety of the surface of the substrate 101, on which the first sourceelectrode 156 and the second source electrode 106, the first drainelectrode 158 and the second drain electrode 108, and the second highpotential supply line 172 b have been formed. Subsequently, theprotective film 166 is patterned through a photolithography process andan etching process using an eighth mask so as to form the pixel contacthole 120. At the same time, the protective film 166 is eliminated fromthe first line contact hole 164.

Referring to FIG. 10I, the first planarization layer 126 is formed onthe substrate 101, on which the protective film 166 has been formed.

Specifically, the first planarization layer 126 is formed in a mannersuch that an organic insulation material such as acrylic resin isdeposited on the entirety of the surface of the substrate 101, on whichthe protective film 166 has been formed. Subsequently, the firstplanarization layer 126 is eliminated from the first pixel contact hole120 and the first line contact hole 164 through a photolithographyprocess using a ninth mask. That is, the first pixel contact hole 120and the first line contact hole 164 are formed so as to penetrate thefirst planarization layer 126.

Referring to FIG. 10J, the pixel connection electrode 142, the secondlow potential supply line 162 b, and the signal link 176 are formed onthe substrate 101, on which the first planarization layer 126 has beenformed.

Specifically, a fifth conductive layer, which is formed of Mo, Ti, Cu,AlNd, Al or Cr, or an alloy thereof, is deposited on the entirety of thesurface of the substrate 101, on which the first planarization layer 126has been formed. Subsequently, the fifth conductive layer is patternedthrough a photolithography process and an etching process using a tenthmask so as to form the pixel connection electrode 142, the second lowpotential supply line 162 b and the signal link 176.

Referring to FIG. 10K, the second planarization layer 128 having thereinthe second pixel contact hole 144 is formed on the substrate 101, onwhich the pixel connection electrode 142, the second low potentialsupply line 162 b, and the signal link 176 have been formed.

Specifically, the second planarization layer 128 is formed in a mannersuch that an organic insulation material such as acrylic resin isdeposited on the entirety of the surface of the substrate 101, on whichthe pixel connection electrode 142, the second low potential supply line162 b, and the signal link 176 have been formed. Subsequently, thesecond planarization layer 128 is patterned through a photolithographyprocess using an eleventh mask so as to form the second pixel contacthole 144.

Referring to FIG. 10L, the anode 132 is formed on the substrate 101, onwhich the second planarization layer 128, having therein the secondpixel contact hole 144, has been formed.

Specifically, a sixth conductive layer is deposited on the entirety ofthe surface of the substrate 101, on which the second planarizationlayer 128, having therein the second pixel contact hole 144, has beenformed. A transparent conductive film and an opaque conductive film areused for the sixth conductive layer. Subsequently, the sixth conductivelayer is patterned through a photolithography process and an etchingprocess using a twelfth mask so as to form the anode 132.

Referring to FIG. 10M, the bank 138, the organic light-emitting stack134, and the cathode 136 are sequentially formed on the substrate 101,on which the anode 132 has been formed.

Specifically, a bank photosensitive film is applied on the entirety ofthe surface of the substrate 101, on which the anode 132 has beenformed. Subsequently, the bank photosensitive film is patterned througha photolithography process using a thirteenth mask so as to form thebank 138. Subsequently, the light-emitting stack 134 and the cathode 136are sequentially formed in the active area AA, rather than in thenon-active area NA, through a deposition process using a shadow mask.

As described above, according to the present disclosure, the firstopening 192 in the bending area and the second source and drain contactholes 110S and 110D are formed through the same single mask process, thesecond opening 194 in the bending area and the first source contact hole160S and the first drain contact hole 160D are formed through the samesingle mask process, the first source electrode 156 and the first drainelectrode 158 and the second source electrode 106 and the second drainelectrode 108 are formed through the same single mask process, and thestorage contact hole 188 and the first source contact hole 160S and thefirst drain contact hole 160D are formed through the same single maskprocess. In this way, the organic light-emitting display deviceaccording to the present disclosure may reduce the number of maskprocesses by a total of at least 4 compared to the related art, therebysimplifying the structure and manufacturing process of the device andconsequently achieving enhanced productivity.

As is apparent from the above description, according to the presentdisclosure, a second thin-film transistor including an oxidesemiconductor layer is applied to a driving transistor of eachsub-pixel, and a first thin-film transistor including a polycrystallinesemiconductor layer is applied to a switching transistor of eachsub-pixel, whereby power consumption is reduced. Further, openingslocated in a bending area and a plurality of contact holes located in anactive area are formed through the same mask process, and thus theopenings and the contact holes are formed so as to have the same depth.Accordingly, the structure and manufacturing process of the deviceaccording to the present disclosure may be simplified, and productivitymay therefore be enhanced. Further, according to the present disclosure,a protective film formed of an inorganic insulation material and a firstplanarization layer formed of an organic insulation material aredisposed between a high potential supply line and a low potential supplyline.

Accordingly, even when a pinhole is formed in the first planarizationlayer, the protective film may prevent short-circuiting of the highpotential supply line and the low potential supply line. Furthermore,according to the present disclosure, a first storage capacitor is formedin a manner such that a second source electrode of the second thin-filmtransistor and a second gate electrode of the second thin-filmtransistor overlap each other with an upper interlayer insulation filminterposed between, or two or three storage capacitors are connected inparallel, leading to an increase in capacitance of the storagecapacitors.

The invention claimed is:
 1. A display device comprising: a flexiblesubstrate comprising an active area and a bending area; a firstthin-film transistor disposed in the active area, the first thin-filmtransistor comprising a polycrystalline semiconductor layer, a firstgate electrode, a first source electrode, and a first drain electrode; asecond thin-film transistor disposed in the active area, the secondthin-film transistor comprising an oxide semiconductor layer, a secondgate electrode, a second source electrode, and a second drain electrode;a first planarization layer covering the first thin-film transistor andthe second thin-film transistor in the active area, the firstplanarization layer extending to the bending area; a connectionelectrode disposed on the first planarization layer; a secondplanarization layer disposed on the first planarization layer includingthe connection electrode in the active area and the bending area; and alight emitting element disposed on the first planarization layer in theactive area, the light emitting element having an anode and a lightemitting stack, wherein the light emitting stack includes at least onelight emitting layer.
 2. The display device of claim 1, wherein thelight emitting stack further includes a charge generation layer, a firstlight emitting stack, and a second light emitting stack facing the firstlight emitting stack with the charge generation layer interposedtherebetween.
 3. The display device of claim 1, further comprising: acolor filter on the light emitting stack.
 4. The display device of claim1, wherein the connection electrode connects one of the first thin-filmtransistor and the second thin-film transistor to the anode.
 5. Thedisplay device of claim 1, further comprising: a signal link between thefirst planarization layer and the second planarization layer in thebending area.
 6. The display device of claim 1, further comprising: abank layer disposed on the second planarization layer, the bank layerdefining a light emitting region, wherein the bank layer includes alight blocking material made of at least one of a color pigment, anorganic black, and carbon.
 7. The display device of claim 1, wherein thesecond gate electrode and one of the second source electrode and thesecond drain electrode overlap each other.
 8. The display device ofclaim 7, further comprising: a light blocking layer overlapping theoxide semiconductor layer and the second gate electrode, wherein thesecond gate electrode and one of the second source electrode and thesecond drain electrode overlap each other to form a first storagecapacitor, wherein the second gate electrode and the light blockinglayer overlap each other to form a second storage capacitor, and whereinthe first storage capacitor and the second storage capacitor areconnected in parallel.
 9. The display device of claim 1, furthercomprising: a plurality of insulating layers comprising an inorganicinsulating material between the first planarization layer and theflexible substrate in the active area; and at least one opening exposinglateral surfaces of the plurality of insulating layers in the bendingarea, wherein the first planarization layer is directly contacted anentire lateral surfaces of the plurality of insulating layers exposed bythe at least one opening.
 10. The display device of claim 1, wherein thefirst and second source electrodes and the first and second drainelectrodes are disposed on a same plane, and the first and second sourceelectrodes and the first and second drain electrodes are made of a samematerial.
 11. The display device of claim 1, wherein the light emittingelement further includes a cathode electrode.
 12. The display device ofclaim 11, further comprising: a low potential supply line connected tothe cathode electrode; and a high potential supply line disposedadjacent to the low potential supply line, wherein at least one of thelow potential supply line and the high potential supply line.